Air leakage testing – the
resistance of the building envelope to inward or outward air leakage. Excessive air leakage testing results in increased energy
consumption and a drafty cold building. Air leakage testing is driven by
differential pressures, across the building envelope. The mechanisms that
create these differences in pressure are the combined effects of – stack
(internal warm air rises), external wind (inducing +ve
and –ve pressures on the envelope) and mechanical
ventilation systems.
Note – Part L1 applies to dwellings, Part L2 to non – domestic buildings. Part L1A and L2A refer to new buildings and L1B and L2B to refurbishments.
The reason the
The Government is committed to
reduce CO2 emissions from energy consumption by 20% by the year 2010. Many of
the buildings constructed today (both dwellings and commercial) consume more
energy than necessary. Two major factors in the design and performance of
building fabric which affect energy consumption are, air leakage testing and
continuity of insulation.
There are also substantial
commercial benefits to building owners that will accrue over the life time of
the building. Reduced energy costs provide clients with real cash incentives to
achieve airtight buildings after air leakage testing. Other benefits are gained
from increased comfort for building users, office staff and / or customers.
Although difficult to total, these are tangible benefits to the client and the
welfare of their respective personnel.
Air Leakage Testing became a requirement under Part
L in April 2002 with a recent update in April 2006. Now, all buildings that
pass through the planning and building control processes have to comply with
Part L this in turn requires YOU the client/contractor to undertake an air
leakage test. The Government is looking to tighten up the regulations and further
updates are due in 2010, this may require all buildings to undertale
air leakage testing. European
Legislation has also been enacted, tightening the use of energy in buildings.
This was introduced in January 2006 through the European Performance in
Buildings Directive.
All parties involved on the project
from the client, contractor and consultants to all site staff and operatives
and off site suppliers need to understand the concepts of air tightness/air
leakage testing and how they affect the part of the project they are involved
with. It only takes one part of the building to be suffer
from air leakage to ensure a failure to comply, which can lead to costly
remedial works and time delays. A real effort needs to be made to educate
everyone involved and ensure that a team effort is made to avoid a failute during the air leakage testing.
ALL buildings require designs to incorporate ‘robust details’ to ensure air
tightness, continuity of insulation and potential problems with thermal
bridging are addressed.
For non domestic buildings, carry out an air leakage testing to ATTMA TS1.
For buildings < 500 m² gross floor area, assume an air permeability rate of
15 to calculate the BER or carry out an air leakage test.
Remember that the maximum air permeability rate is 10 m³/h/m²
at 50 Pascals. However, the air permeability
target may have been set tighter so that the carbon rating is met!!
Key Changes for New Commercial
Buildings Part L2A
Obtaining compliance is now a
five-step procedure.
1. Designers will
need to:
·
Show a
home’s predicted CO2 emission rate will not be greater than the target
emission rate.
·
Ensure
the performance of the building’s fabric, heating, hot water and lighting meets
the minimum values set out in the document.
·
Introduce
passive measures to prevent homes overheating.
·
Ensure
construction is consistent with the design.
·
Provide
the occupier with information to
order to allow the building to be operated as efficiently as possible.
2.
Dwellings now require air
leakage testing
The air permeability of the
envelope should be no greater than 10m³/h/m².
3.
Dwellings will have to produce 20% less CO2 than they do under the
existing regulations.
A carbon comparison must be produced to show how a home’s predicted CO2
emission rate compares to target emission rating based on a national dwelling,
compliant with the 2002 regulations. A fuel factor can be applied to the rating
if LGP, oil mains electricity or solid fuel is used, making it easier to comply
when using these fuels than their carbon content would otherwise allow. So,
with careful design, electric heating can still be used in apartment blocks.
4. There
are two routes to compliance for apartments.
A penthouse does not have to comply with the carbon emission rate provided the
remaining dwellings can compensate, since the compliance for apartment blocks
can be demonstrated either as individual SAP calculations for each dwelling or
as an area-weighted average for all dwellings in the building.
5. A
report should be provided to Building Control
This will identify the features that deliver the CO2 reduction. At
completion, additional schedules covering lighting, robust details and
non-accredited details are required, together with evidence that air
permeability standards have been achieved by passing the air leakage test,
systems have been commissioned and operating instructions issued.
1. More
work is subject to the regulations
The rules will apply to: an extension, a change of use
or alteration, provision of a controlled fitting or service and a provision of
a thermal element.
2. The
route to compliance for an extension has not changed
The elemental route to compliance remains for
extensions and cases where the use of a building has changed.
3.
Individual elements must meet specific standards
Provisions apply to acceptable performance standards for windows, heating and
hot water systems, lighting, insulation of pipes, ducts and mechanical cooling
systems, commissioning and the provision of information.
4. Entire
elements may need to be upgraded
When 25% of a thermal element, such as a roof is upgraded, the entire element
should be upgraded to the latest elemental standards if pay back for the work
can be achieved within 15 years. If not, it should be upgraded to a standard
that does achieve payback within that time.
5. Historic
buildings
Energy efficiency measures should be incorporates where they will not prejudice
the character of the building.
Key Changes for New Domestic Buildings
Part L1A
1.
Obtaining compliance is now a five step procedure
·
The
predicted building CO2 emission rate should be no greater than the
target rate.
·
The
performance of the building fabric, heating and hot water and lighting should
comply with the minimum limits in the document
·
Passive
measures should be included to prevent overheating for areas without cooling.
·
The
building should be built as designed.
·
Provision
should be made to enable energy efficient operation.
2. Air
Permeability /air leakage testing
Air Leakage Tests are required for every building that incorporates a floor
area greater than 500m²
3.
Overheating
Designers must demonstrate that the combined solar and casual heat gains do not
exceed W/m² or that the temperature does not exceed 28C for more than 20 hours
a year spaces with no comfort cooling.
4. Fully
glazed buildings will comply
A typical mechanically cooled and ventilated building, 40% glazed and built to
2002 standards can comply through a combination of omission of roof lights,
improvement in double glazing specification and lighting controls. An
equivalent building with 100% glazed facade could comply with a similar
improvement strategy, but with an additional improvement in the chillier
seasonal efficiency.
5.
Calculating energy consumption
Two calculations are required: a preliminary one, as part of the design commission,
and a final calculation demonstrating compliance based on ‘as constructed’
information, incorporating any performance changes made during construction.
1. More
work carried out to existing buildings is subject to the regulations
An extension, material change of use, material alteration, the provision or
extension of a controlled service or fitting and the renovation of a thermal
element are all now subject to the regulations.
2.
Consequential improvements
Work to existing heating or cooling systems, windows or walls below the element
standards must be upgraded, provided it is technically, functionally and
economically feasible.
3. The
10% rule
The requirement for consequential work is limited to
10% of the value of the principle works. The following elements are all subject
to the 10% rule: any heating, cooling or air handling system older than 15
years should be replaces by new plant and improved controls; any inefficient
lighting system serving more than 100m² should be upgraded; energy metering
should be installed; and if the renewable energy contribution is less than
100%, the system upgraded provided payback is less then seven years.
4.
Extensions
Elemental standards are given for the building fabric and windows in
extensions. There is some flexibility allowed, provided the heat loss for area
weighted U-values is no greater than the equivalent
compliant extension. Extensions over 100m² and greater than 25% of the floor
area of the existing part of the building come under Approved Document L2A
5.
Controlled fittings or services
Compliance is largely elemental,
with specific minimum standards to be achieved. There are additional
requirements governing commissioning, the provision of the sub-meters and log
books
1.
Check the envelope area calculations refer to the whole
building envelope and that this is the envelope that has been actually air
leakage tested.
Has the envelope area been independently verified -
by the architect? Check that the test has been carried out on the same envelope
criteria – i.e. no areas have been excluded for the air leakage test and
included in the calculations.
2.
Check the envelope area calculations refer to the whole
building envelope and that this is the envelope that has been actually air
leakage tested.
Has the envelope area been independently verified -
by the architect?
3.
Check that the test has been carried out on the same
envelope criteria – i.e. no areas have been excluded for the air leakage test
and included in the calculations.
4.
The whole building should be air leakage tested wherever
possible - Not only is the result more accurate but it increases the chance of
the test passing and gaining compliance. If areas have been excluded, are the
reasons valid?
5.
Check that temporary sealing has only been applied to H and
V equipment and other permanently open natural ventilations, otherwise you will
fail the air leakage test
6.
During the air leakage testing, if possible be inside the
building and check-
·
internal
doors are kept open
·
no
additional temporary seals have been added
·
External
windows and doors stay closed
·
Ambient
conditions – wind speed should ideally be a maximum 13 mph
6. The following readings and values should be
checked. Any readings outside the parameters detailed below indicate the test
has been carried out incorrectly and the test should be carried out again.
·
Minimum
6 number readings taken.
·
Or 5 x
the zero flow pressure difference.
·
The
minimum pressure differential should be = 10 Pascals
and maximum pressure differential = 35 Pascals.
·
Correlation
coefficient >0.98, any lower than 0.98 indicates the readings are too far
spread.
·
N has
to lie within the range of 0.5 - 1.0 values outside of
this range indicate that the test has not been carried out properly.
Check the procedures for
the air leakage testing if the building is large and multi-cellular or over 5 storeys tall.
Commercial Benefits to the Building Owner and Client.
One reason only – there are
substantial commercial benefits to having an airtight building and retailers
are accruing those benefits for the life time of the building stock.
A typical example of the real
benefits that can be realised was seen on an existing
retail store that was sealed in February 1997. The ambient temperature in the
store was raised by 5°C, after the store had been air sealed.
Typical air leakage permeability
rates of 3 m³/h/m² have been obtained on new retail
stores and 5 m³/h/m² on existing stores. These levels of air tightness have
been achieved by incremental improvement over a number of years and effort by
all parties involved with the projects.
The additional costs to clients on
new build retail stores is < 0.5% of the total spend.
The real benefits obtained from achieving a good level of air tightness
can be summarised as;
·
Lower
energy costs for the life time of the building
·
Lower
initial capital costs due to down sizing of plant and equipment
·
Air leakage
testing can act as performance tests for fire compartments as well as external
envelopes
·
The
environment within the building becomes less drafty and potentially warmer.
Productivity of staff could be raised significantly - a happy worker is a
productive worker!
·
The
risk of interstitial condensation within the building fabric is minimised, if the building fabric is built to an air
tightness standard. Degradation should therefore be reduced in the long term.
Different types of buildings require different levels of air leakage testing. Air conditioned buildings should be tighter than naturally ventilated ones. Archives, cold rooms and museums will all require to be much tighter to ensure the specification levels for the control of humidity, heat loss and the ingress of pollutants are met.
What is the
Good Practice Guidelines for
Good
Practice Guidelines for
The following figures are recommended air tightness specifications for various
building types as set out in CIBSE TM 23.
|
Air leakage index |
Air Permeability |
m³/h/m² at 50 Pa |
||
|
Practice |
Good |
Best |
Good |
Best |
|
Building Type |
|
|
|
|
|
Office - naturally ventillated
|
10.0 |
5.0 |
7.0 |
3.5 |
|
Offices - balanced mech
vent. |
5.0 |
2.5 |
3.5 |
2.0 |
|
Superstores |
5.0 |
2.0 |
3.0 |
1.5 |
|
Industrial |
15.0 |
3.5 |
10.0 |
2.0 |
|
Dwellings |
15.0 |
8.0 |
10.0 |
5.0 |
Theory Of Air Tightness, Air Leakage Testing and Air Sealing
Measures
Air tightness / air permeability
(air leakage testing) – defined as the resistance of the building envelope to
inward or outward air permeation. Air leakage is driven by pressure
differentials between inside and outside a building caused by the wind, stack
effect and mechanical ventilation systems. Excessive air leakage leads to
increased energy consumption, increased drafts within the building and
increased risks of condensation within the building fabric. For the client, air
leakage testing is physically felt with cold drafts caused by the uncontrolled
movement of air into or out of a building. Cold drafts/air leakage usually
cause complaints from building users!!
Air barrier or air seal line – the physical components that make up the
airtight envelope of the building. The air barrier needs to be continuous
around the whole envelope – roof, walls and ground floors, durable and
maintainable in the long term. The air seal line should be drawn on construction
drawings to communicate the strategy to all relevant parties.
Air tightness test or air leakage testing – the building is air pressure tested
by connecting a fan and measuring the airflow rates required to keep the
building at various positive or negative pressures.
Air permeability – expressed as the amount of air leakage in cubic metres, per hour, per square metre
of envelope at a nominal pressure differential of 50 Pascals,
between inside and outside the building envelope.
Q50 – air flow rate required to pressurise the
building envelope to 50 Pascals, measured unit -
cubic metres per second.
Ensure that all materials and
components used for air tightness purposes have a similar specification and
longevity, as all others used on the project. There is no reason that buildings
constructed to an airtight standard should be stuffy for occupiers or be at
greater risk from condensation. The rule is; build tight – ventilate right there a risk from making a
building envelope too airtight?
No. Part L is meant to control the
amount of uncontrolled air leakage through the building fabric, not the amount
of controlled ventilation.
The target air leakage/permeability
rate of 10 m³/h/m², set down in Part L is achievable
when current best practice for buildings is around 2 m³/h/m². However, if no
regard is taken to air tightness, it is probable that Part L will not be
complied with.
Additional building costs may
amount to 0.5%. This ignores cost savings from down sizing heating plant and
the life time reduction in energy costs.
When a party claims that air
leakage problems will be sorted out after the first air leakage test and will
be remedied then. Air Pressure Testing’s golden rule is that it costs
considerably more to put right second time, rather than doing it right first
time. Ensure that maintenance procedures take air leakage into account. Degradation or damage to
air tight elements or components needs to be minimised
over the long term. We have witnessed how simple it is for an electrician to
punch a large hole through a wall, thereby increasing the air permeability
figure significantly enough for users of the building to complain about an
increase in drafts.
Designing airtight buildings is the
only means of ensuring long term, low air leakage testing performance. Build
tight – ventilate right. The objective is to minimise
uncontrolled air leakage whilst maintaining controlled ventilation. Ensure the
air barrier is based on structural elements, wherever possible. Condensation
risk will be minimised if the air barrier or seal
envelope is correctly positioned, which depends on the make up of the
construction element itself. Generally, it should be placed on the warm side of
the insulation layer. It is also important for the insulation layer to be
continuous and to bear in mind that excessive cold air moving around loose or
misplaced insulation can lead to interstitial condensation.
Ensure that the air leakage testing is carried out by a member of the British
Institute of Non Destructive Testing The DCLG recognises
members as being ‘suitably qualified’ and ‘competent’ companies to carry out
air leakage testing.
Careful consideration is needed on all structural elements.
For instance pre-cast concrete floors may look airtight, but consider air
leakage along open voids through the slab into cavities in external walls! Also
think about non-structural elements such as roof liner sheets or T and G
boarding. A 1mm gap along each joint adds up to a
considerable area for air to leak through. Please download Air Pressure Testings helpful checklist
Where can I access reference to standard details?
·
The
Stationery Office –
·
Kingspan
·
SEDA
·
The
Stationery Office
·
MCRMA
Any supplier of materials or
components who can not state the air leakage rate (permeability) of their
product per meter square, as tested to BS / EN standards. Be forewarned,
material suppliers who states their components are air tight. NO materials are
perfectly airtight, particularly after installation on site!
Using dry lining or vapour barrier as the air barrier is possible with good
detailing. However, a high level of
site supervision is required to ensure all junctions are air tight and that the
lining is not damaged.
Please note: Perforated liner sheets are NOT suitable as an air seal line.
If you have any concerns, request
that the material or component under goes an air leakage test.
Ensure that good, sound building
practice is delivered so that the building is airtight and therefore doesn’t
fail the air leakage testing. If the building is not airtight, the air leakage permeability
target of 10 m3/h/m2 will be exceeded. The end user (–
client) may also find that ventilation is inadequate and may complain of drafts
at times of the year when the building is difficult to heat or cool, an example
of this was bought to our attention when a primary school could not achieve
their minimum operating temperature due to massive amounts of Air Leakage, this
was due to poor design detailing around
the eaves, this resulted in the children being sent home every time the
temperature dropped below the minimum requirement
State clearly in all pricing enquiries the air tightness specification and ask
for details of compliance including specifications, method statements, quality
audits, etc, etc. Ensure a person on site is nominated to control and audit all
aspects of air tightness works, through out the contract period on site. Do not
enclose or cover cavities or gaps before the air tightness works have been
quality assured otherwise the chance of an air leakage testing failure will be
greatly increase
Use similar methods to those used
at present to control all aspects of contracts specification, method statements,
quality management systems, etc. Problems generally occur when responsibilities
for each element or package of work are not clearly defined and agreed, prior
to site work starting.
If the air leakage test fails, how
can air leakage paths be found? A variety of techniques can be used to identify
leakage paths – these include;
·
Feeling
for drafts adjacent to the air barrier, whilst the building is being air
leakage tested. It is useful if the air test fan unit can pressurise
and de-pressurise buildings so that drafts can be
felt for on both the internal and external faces of the air barrier during air
leakage testing.
·
Running
localised smoke tests using a hand held directional
smoke generator.
·
Running
a smoke test on the whole building and undertaking a full photographic survey.
·
Carrying
out a Thermographic survey
·
Physically
checking over the risk areas looking for holes, gaps, etc
Apart from the obvious - unsealed
block work, hollow concrete beams or floor planks, joints/junctions in curtain
walling and dry lining systems, hollow frames/mullions/transoms, hollow steel
sections penetrating the roof or walls, lap joints on roof liner sheets or T
& G boarding - to name a few!
Dividing Q50 by 5.5 gives an
approximate figure for the total leakage area in metres
square. For example; if Q50 = 37 m³/s the total leakage area = 6.7 m².
Treat this figure with respect and care as the visual hole seen on the air seal
line is not always the actual area that air is ultimately leaking from – the
final leakage hole could be a lot smaller.
|
Envelope |
Leakage Rates (m3/hr
at 50Pa) |
|||||
|
|
5 |
7.5 |
10 |
15 |
20 |
25 |
|
2000 |
0.51 |
0.76 |
1.01 |
1.52 |
2.03 |
2.54 |
|
5000 |
1.27 |
1.90 |
2.54 |
3.80 |
5.07 |
6.34 |
|
7500 |
1.90 |
2.85 |
3.80 |
5.71 |
7.61 |
9.51 |
|
10000 |
2.54 |
3.80 |
5.07 |
7.61 |
10.14 |
12.68 |
|
12500 |
3.17 |
4.75 |
6.34 |
9.51 |
12.68 |
15.85 |
|
15000 |
3.80 |
5.71 |
7.61 |
11.41 |
15.21 |
19.02 |
|
20000 |
5.07 |
7.61 |
10.14 |
15.21 |
20.29 |
25.36 |
|
Leakage
Rates (m3/hr) by Area (m2) |
||||||
Any sub contract package is
proposing to use gaffer tape or plastic sheeting to air seal works. Can we do
the air leakage testing next Tuesday, if the roof plant comes tomorrow and the
fitters come in on Sunday to install it? NO! Plan ahead and ensure the building
is ready for the air leakage test. Ensure the size – flow rate of the fan is
adequate for the job. Ask for calculations to back this up.
Ventilate right – the main
contractor should build the envelope tight. This will enable the design,
specification and sizing of the heating and ventilation system to be carried
out with confidence. Fresh air openings in the envelope constitute
massive air leakage paths and will ensure buildings fail the air leakage testing.
Check the envelope area is correct.
What BS or EN standards are air leakage pressure tests carried out to?
ATTMA TS1 & BS EN 13829:2001(1)
Thermal Performance of Buildings: Determination of air permeability of
buildings – Fan pressurisation method.
For a moderately sized single
storey building which complies with Part L, Qleakage
= <10 m³/h/m², the average ventilation rate will be approximately 0.3 ach.
The ventilation rate in ach can be approximately estimated as A/(6*S) ach where A = Area of walls, roof and ground floor
and S = area of walls and roof.
Qleakage = rCp
* V * n / 3600 W/K where rCp heat capacity of air, V volume of building m³ and n
is the ventilation rate in air changes per hour - ach.
For an industrial building with a
floor area of 5000 m2, currently built without air tightness considerations;
air permeability can be > 14 m³/h/m². This equates to a hole in the roof of
approximately 5 m²!!
If the air permeability can be
reduced to 8 m³/h/m², which comfortably passes Part L, then the energy saving
could equal > 60,000 kWh per annum. NOTE. Current best practice for
industrial type buildings in regards of air tightness is an air permeability
figure of 2 m³/h/m².
Services can be routed through
ducts inside the building envelope. Sealing multiple service penetrations is
awkward but similar principles to those used to seal penetrations through fire
walls and plant room slabs should be used.
ATTMA TS1 states that the fan
should be able of achieving > 80% of the required air flow rate at 50 Pascals pressure difference.
Set our clearly in all
documentation the level of air tightness that can be achieved and how it is to
be practically achieved on site prior to air leakage testing. Be specific about
whose responsibility it is to seal components and also adjacent elements,
including works on site. Show these details clearly on all contract and site
drawings and ensure that specified materials and components are fit for
purpose.
Ensure all site staff and
operatives fully understand the concepts of air tightness and air leakage
testing the details of how it is to be achieved on site. Ensure training is
carried out for all the parties involved, including site operatives.
Components could be tested in
laboratories or tested on site in specially built enclosures as specified in BS
EN 12114:2000. The test method allows the air leakage testing through
individual joints to be derived. From this information the building air leakage
rate can be estimated by totaling up the leakage rates for all the joints in
the building envelope.
As with all gaps and joints, there
are many BS EN Standards which specify in detail, how they can be bridged
effectively. Materials not to use include materials permeable to air (e.g.
mineral fibre) or flimsy sheets, thin gaffer tapes or
similar are not suffient materials to seal against
Air Leakage. Sealant, expanding foam and tapes can be used, if specified and applied correctly. Ensure
that all materials and
components are fit for purpose and installed to current standards.
If there is no information on air
leakage rates for materials or components, there can be no confidence with the
final performance on site. Obtain a component air leakage test – contact Air Pressure
Testing Ltd for details.
Many modern construction systems and designs rely on gaskets or sealants within
the joint to seal the system. If these are not installed correctly during
installation, the air leakage could be considerable, and subsequently the
building may fail the air leakage test
A typical example is with block
work. Well designed, specified and constructed block work (with full horizontal
and perpendicular joints)can achieve a very good
standard with air leakage < 2
m3/h/m2. However, without taking due regard can lead some block work
walls to have high leakage rates - for a variety of reasons. Sometimes blocks
are not specified with an air leakage rate and also the composition and leakage
testing rates of identical blocks, manufactured in different plants, can vary
significantly.
On site problems with quality of
block work and mortar joints can lead to significant leakage during the air
leakage testing. For example, where block work is concealed above suspended
ceilings, vertical mortar joints – perps – may not be
filled completely but ‘faced up’, which leak, this is where on site audits are
at their most effective as they pick up on problems such as this at the
construction phase
Ensure that the air leakage testing is carried
out by a member of BINDT (The British
A building will fail Part L if the air permeability rate is
> 10 m³/h/m². More stringent requirements may be in place, depending
on the requirements within the building energy calculation to satisfy the
carbon emissions target.
If Buildings also fail
Thermographic inspections of the visible envelope, it will show that insulation
is not reasonably continuous.
ATTMA TS1 states that fan flow
rates should be measured to ± 7%.
The accuracy of the air leakage testing itself will
be affected by the strength and gustiness of the wind. The wind will
impose both positive and negative pressures on the building envelope, which
will vary during the test. ATTMA TS1 states that tests should normally only be
carried out when wind speeds are below 6 m/s. Occasionally a test may
have to be carried out in wind speeds above this. Decisions will be made
on a job specific basis. When Wind speed conditions are close to the maximum
permitted Air Pressure Testing will use their Wind damping kits to ensure that
accurate readings are undertaken at all times
Use the same principles of design
and construction as for other air tightness works but use fire rated materials.
Compliance to various sections of Part L1 and L2 can be achieved by a
‘competent person’ reviewing the design and/or site works and deeming them
adequate. These Sections include air tightness for buildings and continuity of
insulation for all buildings. Air Pressure Testing Ltd can take on this role
and issue the necessary declaration to the Building Control Officer.
Air Pressure Testing Ltd Services Ltd has
air leakage testing equipment suitable
for testing buildings with floor areas from 10
to 40,000 square metres. For the
easiness of portability Air Pressure Testing Ltd use their Retrotec
3001 portable high power systems which are 710 mm diameter fans which can be
built into sets of up to 3 fans. These are electrically powered, quiet, clean and as the name suggests portable. They can easily
test whole buildings or if necessary be erected inside buildings to undertake
air leakage testing on plenums, service
ducts, fire compartments, upper storey’s, extensions, etc, etc.
To
undertake air leakage testing on larger buildings Air Pressure Testing can link
up to 6 of their Retrotec 3001 3 fan systems this
allows us to undertake air leakage testing on buildings upwards of 40,000 Metres, this reduces the need for large trailer fans that
can prove to be disruptive to sites with tight access such as city centre’s,
when other Air Leakage Testing companies state that they haven’t the equipment
to test your building, you know where to come.
Carry out the air leakage testing
when the building envelope is complete. Temporarily sealing areas of the
building is not only difficult and costly to do well, but the risk of failing
increases as well. It is far better to delay the test for a week rather than undertaking
the air leakage testing too early, fail, and then have to carry out another air
leakage test in one weeks time.
Temporarily seal all heating and
ventilation equipment and ensure window trickle ventilators are closed. Check
all service ducts (including telephone, electric, spare ducts) and water and
condensate traps are either sealed or full.
The
worst acceptable standard for the leakage testing rate is < 10 m³/h/m²
No. A heavy thunderstorm may impose
pressures of 500 Pascals onto the building fabric, so
air leakage testing will not cause any structural damage
A minimum of 4 hours should be
allowed to carry out an air leakage test. It will take approximately 1-2 hours
to temporarily seal services, however if the client/customer is proactive and
the sealing works are undertaken before we visit site the actual air leakage testing
time can be greatly. If the air leakage test runs smoothly, a maximum of 30
minutes is required; but it’s best to allow 1 hour. It takes approximately 1
hour to de-rig all of our air leakage testing equipment. However, if an air leakage
testing fails and multiple air leakage tests are carried out or the fan is left
running to search for drafts and air leakage paths, then the air leakage testing can run over
the usual 2-3 hrs
Yes, as long as no-one opens a door
or access hatch which will obviously compromise buildings air barrier – which
basically allows the air pressure to drop and the air leakage testing would
need to be run again.
Does the smoke test damage the
building?
No. However, the building needs to
be empty of all people for Health and Safety reasons due to the poor
visibility. It is also essential you inform the Fire Brigade to avoid
unnecessary call outs. The smoke is a harmless food grade water based
mono-propylene glycol (MPG), but it is a good idea not to expose fresh food or
produce to it.
ATTMA TS1 states that the fan must
be capable of achieving at least 80% of the required air volume flow rate, at
50 Pascals pressure difference – Q50. Q50 = A * 10 /
3600 m³/s where 10 is the Air Permeability target, A = Area of walls, roof and
ground floor
Note. Air
Pressure Testings 3001 series fans can deliver from 1
- m³/s to over
70 m³/s so capacity is not a problem
Air Pressure Testing Ltd offer wide
ranging technical and practical construction experience of building technology,
design issues and potential faults in buildings allows us to give a high level
of service both in carrying out the survey and interpreting the results.
Building thermography
is an effective method of indicating the heat distribution over the surface of
a building envelope. This remote-sensing technique can be carried out with
minimal disturbance by a single operator and allows qualitative detection of
air leakage pathways and insulation discontinuities. The survey will be carried
out using an un-cooled thermal imaging camera, which can measure temperatures
to 0.1°C and displays the images and reports in full colour.
Air Pressure Testing uses a calibrated FLIR camera, which allows full analysis
of saved images.
Thermographic Surveys are carried
out to BS EN 13187:1999: Thermal
performance of buildings - qualitative detection of thermal irregularities in
building envelopes - infra-red method and BRE Report 176 - A Practical Guide to
Infra-Red Thermography for Building Surveys.
Please click here to down load a copy
The following outlines the
requirements for the above test. Areas of discontinuous insulation will be more
readily identified in these conditions:
An hand-held infra-red sensitive camera
records images of the subject that are compared to conventional pictures of the
same areas. "Hot-spots" can then be related to features of the
building and an informed view taken of building integrity. Local/component thermography whilst a building is depressurised
can identify where air tightness needs improving.
You must ensure there is a minimum
temperature differential between inside and outside the building of at least
10°C. This is usually achieved by leaving the heating system turned on inside
the building for 12 – 24 hours prior to the survey.
Carry out external Thermographic
surveys after dark (or heavy cloud), to ensure problems with sunlight warming
up external surfaces can be ignored. Ensure the weather is dry as moist
surfaces play havoc with the survey results. Beware items of plant emitting
heat inside a building, as they can affect the results.
A thermal image makes it easy to
identify areas of missing, misplaced or discontinuous insulation.
It can also be used to identify air leakage paths if used correctly. Cold air
leaking into a building will cause cold patches on the surrounding fabric,
which can be identified from thermal images.
No, but they provide a qualitative
appreciation of the thermal properties of a building envelope, quickly over
large areas and display the results graphically in colour.
Spot temperatures are also measured which can allow for later analysis of the
thermal performance of building envelopes, again especially useful in
highlighting areas of misplaced or discontinuous insulation, something Air
Leakage Testing cannot
How can you interpret the thermal
images?
A sound knowledge of construction
technology and a sound knowledge of the projects design (U values, emissivity of materials) allied with experience of on site
defects is required to identify the true cause of
faults identified on site. Particular care needs to be taken with regard to the
emissivity and reflectivity of surfaces. Surfaces
with low emissivity (e.g. polished steel), appear colder than their surroundings but
are sensitive to reflective heat from background sources e.g. equipment,
lights, people etc.
If the thermal image of the inside
face of a building envelope appears to have a low surface temperature compared
to their surroundings. Take care to evaluate the results as this could be
caused by;
·
Missing
or damaged insulation or maybe high levels of moisture within the building
fabric
·
High
levels of air leakage cooling the inside face
·
Thermal
bridging
·
Evaporation
of moisture from the internal surface
·
Cold
rooms inside the building cooling the surroundings
To ensure the air leakage testing
is carried out to plan and the risk of failing is minimised,
it is necessary for Air Pressure Testing and the client to work together. Once
Air Pressure Testing receives an order, a procedure is set into train which
ensures that everything swings into action. At least a week prior to the air leakage
testing, Air Pressure Testing send clients a checklist of procedures which the
client needs to confirm that they are ready for the air leakage test. Please find attached checklist
The e-mail/fax back includes the following points;
1. Air leakage test time
and date must be established. Note, the client can
change the date of the air leakage test up to 72 hours prior to the test
without charge. Air Pressure Testing must be informed at least 5 days prior to
the air test of any major temporary works, as these may adversely affect the
result of the air leakage test.
2. Access to the door where the fan is to be set up, should be flat and
accessible.
3. Air Pressure Testing set up the screen for the fan if